linux-kernel - Re: [PATCH v13 02/17] preempt: Reduce NMI_MASK to single bit and restore HARDIRQ

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Message-ID: <87ecqe8049.fsf@t14s.mail-host-address-is-not-set>
Date: Tue, 04 Nov 2025 13:15:34 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Lyude Paul <lyude@...hat.com>, rust-for-linux@...r.kernel.org, Thomas
 Gleixner <tglx@...utronix.de>, Boqun Feng <boqun.feng@...il.com>,
 linux-kernel@...r.kernel.org, Daniel Almeida
 <daniel.almeida@...labora.com>
Cc: Joel Fernandes <joelagnelf@...dia.com>, Ingo Molnar <mingo@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann
 <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben
 Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Valentin
 Schneider <vschneid@...hat.com>
Subject: Re: [PATCH v13 02/17] preempt: Reduce NMI_MASK to single bit and
 restore HARDIRQ_BITS

Lyude Paul <lyude@...hat.com> writes:

> From: Joel Fernandes <joelagnelf@...dia.com>
>
> Now that NMI nesting is tracked in a separate per-CPU variable
> (nmi_nesting), we no longer need multiple bits in preempt_count
> for NMI tracking. Reduce NMI_BITS from 3 to 1, using it only to
> detect if we're in an NMI.
>
> Signed-off-by: Joel Fernandes <joelaf@...gle.com>
> Signed-off-by: Lyude Paul <lyude@...hat.com>

The commit summary is mentioning HARDIRQ_BITS, but I don't think that
change is part of this commit.


Best regards,
Andreas Hindborg